There are many prior art disposable garments for infants and incontinent adults, including, without limitation, diapers and training pants. In most of such garments, elastic is used to improve the fit of the garment on the wearer, particularly in the leg and waist areas. Such elastic is most often incorporated in such disposable garments by gluing or otherwise fixing homogenous strands of elastic into the disposable garments.
One of the problems with using elastic to improve the fit of disposable garments is properly adjusting the tension of the elastic to maximize fit and comfort. In assembly-line construction of disposable garments, it is not economically feasible to vary the diameter or tensile strength of the elastic if the elastic is a homogeneous strand dispensed from a roll. It is not feasible to adjust the tension of such elastic as it is incorporated into the disposable garment, because to do so would require high speed, precisely coordinated variation in the stretch of the elastic as it is fixed to the disposable garments on the assembly line. Disposable garments often have elastic strands where elastic strands are wholly undesirable, such as the crotch area, because economy and efficiency require that the elastic strands be continuous as they are dispensed along a web on an assembly line. Accordingly, prior disposable garments incorporating elastic often have areas in which the elastic is too tight to maximize the utility of the garment or so tight as to cause undesired discomfort. To avoid such excessive tightness, the elastic may be applied generally to the garment with such little tension that the garment has areas in which the elastic is too loose to maximize the utility of the garment.
For example of excessive tightness, diapers or training pants may have a continuous elastic chord that encircles the garment leg openings and crosses at the crotch area. In such garments, the elastic crossing at the crotch area tends to be of such high tension that the crotch becomes hard and uncomfortable. Such elastic at the crotch area also pulls the edges of the leg openings at the crotch away from the wearer's skin, causing any discharge from the wearer to leak from the garment. Further, such elastic at the crotch area tends to invert the absorbent core at the crotch, causing the core to assume a convex shape from the perspective of the wearer's crotch. Such inversion undesirably causes discharge to run from the surface of the core toward the leg openings of the garment.
To adjust the tension of elastic in disposable garments, the prior art teaches that multiple elastic strands may be used in parallel. To reduce the collective tension of the parallel elastic strands, the distance between the parallel strands may be widened, thus dissipating over a wider area the contractive force of the strands. The foregoing method, however, requires precision orientation of the strands. Further, the foregoing method is of limited effectiveness for varying tension, since the tension can only be dissipated over a widened area, not eliminated.
For the foregoing reasons, it is an object of the present invention to provide a method and apparatus for effectively varying the elastic stress of elastic disposed within a disposable garment. It is a further object of the present invention to reduce the tension of elastic strands crossing at the crotch area of disposable garments.